POC alternate callback syntax

Zend/tests/class_name_as_scalar.phpt

@@ -2,6 +2,7 @@
 class name as scalar from ::class keyword
 --FILE--
 <?php
+// Keep in sync with fn_callbacks/class_name_resolution.phpt
 
 namespace Foo\Bar {
     class One {

Zend/tests/fn_callbacks/basic.phpt

@@ -0,0 +1,80 @@
+--TEST--
+fn:: callback basic usage
+--FILE--
+<?php
+
+namespace Foo\Bar {
+    class One {
+        function getThisCallback() {
+            return fn::$this->meth;
+        }
+    }
+    function baz() {
+        return 'Foo.Bar.baz';
+    }
+    function qux() {
+        return baz();
+    }
+
+    echo "Static\n";
+    var_dump(fn::One::method); // resolve in namespace
+    var_dump(fn::\One::mEtHod); // resolve fully qualified
+
+    echo "Dynamic\n";
+    $one = new One();
+    var_dump(fn::$one->meth);
+    var_dump($one->getThisCallback());
+    var_dump($one === $one->getThisCallback()[0]);
+
+    echo "Function\n";
+    var_dump(fn::intval);
+
+    // TODO implement name resolution
+    //var_dump(fn::baz);
+}
+
+namespace {
+    use function Foo\Bar\baz, Foo\Bar\qux;
+    var_dump(fn::iNtVal);
+    var_dump(fn::Foo\intval);
+
+    // TODO implement name resolution
+    //var_dump(fn::baz);
+    //var_dump(fn::qux);
+}
+
+?>
+--EXPECT--
+Static
+array(2) {
+  [0]=>
+  string(11) "Foo\Bar\One"
+  [1]=>
+  string(6) "method"
+}
+array(2) {
+  [0]=>
+  string(3) "One"
+  [1]=>
+  string(6) "mEtHod"
+}
+Dynamic
+array(2) {
+  [0]=>
+  object(Foo\Bar\One)#1 (0) {
+  }
+  [1]=>
+  string(4) "meth"
+}
+array(2) {
+  [0]=>
+  object(Foo\Bar\One)#1 (0) {
+  }
+  [1]=>
+  string(4) "meth"
+}
+bool(true)
+Function
+string(6) "intval"
+string(6) "iNtVal"
+string(10) "Foo\intval"

Zend/tests/fn_callbacks/class_name_resolution.phpt

@@ -0,0 +1,54 @@
+--TEST--
+fn:: callback with static classname
+--FILE--
+<?php
+// Keep in sync with class_name_as_scalar.phpt
+
+namespace Foo\Bar {
+    class One {
+    }
+    class Two extends One {
+        public static function run() {
+            var_dump((fn::self::meth)[0]); // self compile time lookup
+            var_dump((fn::static::meth)[0]); // runtime lookup
+            var_dump((fn::parent::meth)[0]); // runtime lookup
+            var_dump((fn::Baz::meth)[0]); // default compile time lookup
+        }
+    }
+    class Three extends Two {
+    }
+    echo "In NS\n";
+    var_dump((fn::Moo::meth)[0]); // resolve in namespace
+}
+
+namespace {
+    use Bee\Bop as Moo,
+        Foo\Bar\One;
+    echo "Top\n";
+    var_dump((fn::One::meth)[0]); // resolve from use
+    var_dump((fn::Boo::meth)[0]); // resolve in global namespace
+    var_dump((fn::Moo::meth)[0]); // resolve from use as
+    var_dump((fn::\Moo::meth)[0]); // resolve fully qualified
+    Foo\Bar\Two::run(); // resolve runtime lookups
+    echo "Parent\n";
+    Foo\Bar\Three::run(); // resolve runtime lookups with inheritance
+}
+
+?>
+--EXPECT--
+In NS
+string(11) "Foo\Bar\Moo"
+Top
+string(11) "Foo\Bar\One"
+string(3) "Boo"
+string(7) "Bee\Bop"
+string(3) "Moo"
+string(11) "Foo\Bar\Two"
+string(11) "Foo\Bar\Two"
+string(11) "Foo\Bar\One"
+string(11) "Foo\Bar\Baz"
+Parent
+string(11) "Foo\Bar\Two"
+string(13) "Foo\Bar\Three"
+string(11) "Foo\Bar\One"
+string(11) "Foo\Bar\Baz"

Zend/zend_language_parser.y

@@ -243,6 +243,7 @@ static YYSIZE_T zend_yytnamerr(char*, const char*);
 %type <ast> exit_expr scalar backticks_expr lexical_var function_call member_name property_name
 %type <ast> variable_class_name dereferencable_scalar constant dereferencable
 %type <ast> callable_expr callable_variable static_member new_variable
+%type <ast> callback callback_expr
 %type <ast> encaps_var encaps_var_offset isset_variables
 %type <ast> top_statement_list use_declarations const_list inner_statement_list if_stmt
 %type <ast> alt_if_stmt for_exprs switch_case_list global_var_list static_var_list
@@ -884,6 +885,8 @@ new_expr:
 expr:
 		variable
 			{ $$ = $1; }
+	|	callback
+			{ $$ = $1; }
 	|	T_LIST '(' array_pair_list ')' '=' expr
 			{ $3->attr = ZEND_ARRAY_SYNTAX_LIST; $$ = zend_ast_create(ZEND_AST_ASSIGN, $3, $6); }
 	|	'[' array_pair_list ']' '=' expr
@@ -1124,6 +1127,42 @@ scalar:
 	|	constant			{ $$ = $1; }
 ;
 
+callback:
+		T_FN T_PAAMAYIM_NEKUDOTAYIM callback_expr    { $$ = $3; }
+;
+
+callback_expr:
+		T_VARIABLE T_OBJECT_OPERATOR T_STRING {
+			$$ = zend_ast_list_add(
+				zend_ast_create_list(
+					1, ZEND_AST_ARRAY,
+					zend_ast_create(
+						ZEND_AST_ARRAY_ELEM,
+						zend_ast_create(ZEND_AST_VAR, $1),
+						NULL
+					)
+				),
+				zend_ast_create(ZEND_AST_ARRAY_ELEM, $3, NULL)
+			);
+		}
+	|	class_name T_PAAMAYIM_NEKUDOTAYIM T_STRING {
+			$$ = zend_ast_list_add(
+				zend_ast_create_list(
+					1, ZEND_AST_ARRAY,
+					zend_ast_create(
+						ZEND_AST_ARRAY_ELEM,
+						zend_ast_create(ZEND_AST_CLASS_NAME, $1),
+						NULL
+					)
+				),
+				zend_ast_create(ZEND_AST_ARRAY_ELEM, $3, NULL)
+			);
+		}
+	|	name {
+			$$ = $1;
+		}
+;
+
 constant:
 		name { $$ = zend_ast_create(ZEND_AST_CONST, $1); }
 	|	class_name T_PAAMAYIM_NEKUDOTAYIM identifier